1. Field of the Invention
The present invention relates to an inkjet recording device which ejects ink liquids of plural colors and a reaction liquid, which causes a predetermined reaction to occur at the ink liquids, for recording an image at a recording medium.
2. Description of the Related Art
Heretofore, inkjet recording devices (“inkjet printers”) have been known which eject ink droplets of plural colors (for example, black (K), cyan (C), magenta (M) and yellow (Y)) from droplet ejection heads to form color images at recording mediums such as paper and the like.
In this kind of inkjet recording device, halftone processing is performed in accordance with gradation values of each of pixels of image data. A pixel may be recorded by plural dots, and image quality of an image may be improved by controlling ejection amounts of ink droplets, which are ejected from the droplet ejection heads to each of the dots constituting the pixel, to, for example, “large droplet”, “medium droplet”, “small droplet” or “null”, to control the sizes of the dots that are recorded. Now, Japanese Patent Application Laid-Open (JP-A) No. 2001-105633 has disclosed, for an inkjet recording device which is capable of recording dots of plural sizes, a technique of recording the color Y with smaller dot sizes, because, in the color Y, streaking and color variation are less conspicuous relative to the colors K, C and M.
Further, at this kind of inkjet recording device, in addition to the ink liquid of each color, a reaction liquid may be provided for, for example, coagulating dye of the ink to prevent running of the ink, or improving coloration characteristics of the ink or the like. In JP-A No. 58-128862, a technique has been disclosed in which this reaction liquid (described as a processing ink in JP-A No. 58-128862) is ejected to overlay an image, improving image quality of the recorded image.
However, in a case of controlling ejection amounts of ink liquids ejected from droplet ejection heads to large droplet, medium droplet, small droplet and nothing, as described above, it is necessary to perform control of the droplet ejection heads with two bits of data (for four values) being prepared for each dot for each color to be recorded. Therefore, in order to eject C, M, Y and K ink liquids and a reaction liquid from the droplet ejection heads for recording a color image, ten bits of dot data are required for each dot, and the data amount for one dot does not constitute a single byte (eight bits). Consequently, it is more difficult to perform various kinds of digital processing on the respective dots of the dot data, which is problematic.